1. Field of the Invention
The present invention relates to an operation control system for starting and monitoring FA (Factory Automation) equipment such as a robot, a conveyor, and the like, and for systematically operating such FA equipment.
2. Description of the Related Art
Sequence control is a basic technique in automation, and is widely used in various industrial and social phases. For example, FIG. 1 shows a conventional system when a predetermined product is assembled using a robot. Robot 1, conveyor 3, and visual sensor 5 are respectively connected to and controlled by robot controller 7, programmable controller 9, and visual sensor controller 11. Controllers 7, 9, and 11 exchange with each other information of operational states of robot 1, conveyor 3, and visual sensor 5, so that robot 1, conveyor 3, and visual sensor 5 are controlled so that they operate in association with each other.
In the system described above, hand 13 of robot 1 is imaged and monitored by visual sensor 5, and information from sensor 5 is supplied to controllers 7 and 9. As a result, robot 1 executes a predetermined task in relation to parts 15 conveyed along conveyor 3, and assembles a product.
In this system, robot controller 7 is programmed in a robot language, and programmable controller 9 is programmed in a PC (Programmable Controller) language. This difference in program languages is disadvantageous from the point of view of exchange of operational state information among controllers 7, 9, and 11, rendering such exchange undesirably difficult. Thus, when a new item of FA equipment is added, and the control programs of controllers 7, 9, and 11 must be updated accordingly, this can only be done with considerable difficulty. As a result of the developments occurring in recent years, with regard to programmable controllers, computers, and the like, as well as the increase in the size of objects being controlled, control systems have tended to become increasingly complicated. In this case, the system has simultaneous and parallel characteristics, and phenomena such as an inoperable state, contention, overrun, and the like which do not occur in a system with a relatively simple structure may occur.
In order to solve the above softwave-related problem, a software system for an industrial sequence controller has been proposed. In "Proposal of Mark Flow Graph for Discrete System Control" by Kensuke HASEGAWA, Koji TAKAHASHI, Ryosuke MASUDA, and Hidemine OHNO in "Keisoku Jido-seigyo Gakkai Ronbunshu" VOL. 20, NO. 2, 1984, the Mark Flow Graph is proposed as a graphic technique effective for theoretically systematizing sequence control based on the Petri Net.
In "A Petri Net-Based Controller for Flexible and Maintainable Sequence Control and its Applications in Factory Automation" in IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS VOL. IE-33, No. 1, Feb. 1986, a Petri Net-based controller is described.
However, according to a method for providing operation conditions using the Petri Net to execute FA equipment control, a network of the entire system must be constituted to clearly define all the FA equipment and all the states to be controlled. In addition, in order to describe the Petri Net, a user must be skilled in the creation thereof.
When the FA equipment are controlled, a robot may have intelligence so that it can be controlled by a rough command, requiring only a high-level control. However, low-level control must be performed for a hand and switches. Thus, levels of objects to be controlled are different. Therefore, when FA equipment is controlled using on command interpreter, the structure of the command interpreter is inevitably complicated. In addition, each time a new item of FA equipment is added, the entire command interpreter must be rewritten.